Silicon Oxide-Encapsulated Platinum Thin Films as Highly Active Electrocatalysts for Carbon Monoxide and Methanol Oxidation

Direct alcohol fuel cells (DAFCs) have the potential to provide high power densities for transportation and portable applications. However, widespread use of DAFCs is greatly hindered by the lack of anode electrocatalysts that are inexpensive, stable, resistant to CO poisoning, and highly active toward alcohol oxidation. One promising approach to overcoming these challenges is to combine transition metal catalysts with oxide supports, such as SiO2, which are known to enhance alcohol oxidation by promoting CO oxidation at oxidelmetal interfacial regions through the so-called bifunctional mechanism. Herein, we report on a membrane-coated electrocatalyst (MCEC) architecture for alcohol oxidation, in which a thin, permeable silicon oxide (SiOx) nanomembrane encapsulates a well-defined Pt thin film (SiOx vertical bar Pt). A key advantage of the MCEC design compared to oxide-supported nanoparticles is that the oxide encapsulation maximizes the density of oxidelmetal interfacial sites between the SiOx and Pt catalyst. A series of electroanalytical measurements indicates that the SiOx overlayers provide proximal hydroxyls, in the form of silanol groups, which can enhance alcohol oxidation by interacting with adsorbed intermediates at SiOx vertical bar Pt interfaces. Thanks to these interactions, the SiOx vertical bar Pt electrocatalysts exhibit significantly enhanced CO oxidation activity and roughly a 2-fold increase in the maximum methanol oxidation current density compared to bare Pt. Overall, these demonstrations highlight the potential of using SiOx-based MCECs for CO tolerant and highly active methanol oxidation electrocatalysts.